Version of Windows Already Installed Error

[SomeGuy1]

You need to format the system and boot partition before installing.

Hi, I did format a volume several times. Take a look at the attached screen shot showing how drive looks from the Disk Mgmt console and in WinUSB.

Not sure what else I need to do to use the disk ?
Thanks !

I encountered a similar thing when I was attempting to use WinToUSB on an external USB HDD that had a previous Win8.1 installation on it.

I used an application called AOMEI Partition Assistant to format the partitions on the external USB drive. I then attempted to use WinToUSB to copy the existing Win8.1 installation on the internal HDD to the external HDD and got that error message.

I then used DiskPart from the command line to prepare the external HDD, and after that, WinToUSB ran just fine and did not generate that error message.

Try this:

Open an Administrator level Command Prompt.

Start Diskpart.

"List" your drives
"Select" your external USB drive

clean
convert gpt
list partition
select (the MSR partition that was automatically generated)
delete partition override
create partition efi size=260
format quick fs=fat32
create partition primary
format quick fs=ntfs